Far Cry Demo problems

The farcry demos used to work on my rig a while ago (when they first came out), recently I reinstalled them because I've been rather obsessed with wanting to buy it annnnnd they won't work, no matter where I download them from. When I try to play the first demo I get the following 2 error messages:

the lower of the error messages comes immediately after I click OK on the first error.

EDIT: first error has been solved. Reinstall fixed it, unfortunately it now crashes every 2 minutes into the game, running on all medium settings on a Geforce Ti4200. Wtf.

THe next error comes while trying to install the Research demo. As soon as the installation is about to begin I see:

I'll try uninstalling and reinstalling but I've jsut never had this sort of thing happen before sooo if anyone has any suggestions they are welcome

Yeah, I got a message something like that too just now when I tried to install the game. It still installed, though, but when I ran the demo, all the settings were stuck on low and couldn't be set any higher for some reason. I've a 6600 GT and my former card (5200) ran it with all the settings up, even though it ran sluggish at most times. What the sandpaper, like. First of all I'm having trouble running the Nalu and Clear Sailing graphics demo's, now Far Cry is sandpapered up. :rant:

Mike did you tried red/l the demo again ?

and Stiofain that could be a driver problem perhaps ?

X, I've downloaded both demos from 2 seperate credible places (fileshack, filefront etc)

well ill go try it now and see if it doesnt crash a minute or 2 into it. really wish the Research dmeo would work though. I've already played through the first many times